[Mini-Tutorial] Iray Progressive Render Settings

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SickleYield's avatar
This weekend I got a chance to talk to the DAZ 3D developers about the progressive render settings and what they do.  Here's some clarification on those settings.  I did not know some of this myself until I had a chance to ask this weekend!

The progressive render settings are found in the "Render Settings" tab in DAZ Studio and the "Editor" portion of that tab.  The important settings are:

Max Samples:  Short version: The Max Samples count is the maximum number of samples Iray will achieve before it stops the render.  The default number is 5000.  How long it takes to get to 5000 samples varies by what kind of hardware your computer has - it will get to 5000 much faster on an Nvidia graphics card than a CPU or an AMD card.

Longer version, as best I was able to learn from web research: In any kind of rendering, the engine is trying to depict a 3D image as though it were in real space; in real space your eye views all images as continuous, but in the rendered image, the image has to be broken up into a finite number of pixels.  The process of sampling is how a render engine tries to compensate for working with those pixels and the fact that visual information "stops" between them, creating the visual artifacts that you probably associate with a "bad" Iray render.  But importantly for now, the more samples Iray calculates, the more it can smooth out the 3D space between the pixels into a continuous image without "jaggies" or "fireflies."  More samples make a smoother, more complete image. 

Max Time (secs):  Iray can also be told to stop the render when a certain number of seconds have passed.  The default value is 7200, which is two hours.

Important take-away: Iray will quit when it gets to ONE of these two values, normally.  If it gets to two hours but has only done 2000 iterations or samples, it will still quit.  If you have older or lesser hardware, you need to set the time much higher to get the same samples.

Rendering Quality Enable:  If this is set to OFF, Iray will just use the Max Samples and Max Time to determine when render stops.  If you want render time to go just based on those, turn this to OFF.  If it is off, the Quality and Convergence sliders don't matter.

Rendering Quality: This linearly increases render time each time you raise the number: 2 is double the value of 1, 3 is triple the value of 1, etc.  It overrides the time and samples counts.  Use this only if you really want to try the "render forever and tell it to stop when I like how it looks" method.  Otherwise just leave it at 1.

Rendering Converged Ratio:  This is a function of the time and samples counts.  I did not realize this until a dev told me, but apparently this is actually impossible to get to 100%, so to avoid errors it's better to converge to 99.9% instead if you want to make sure everything runs long enough without resorting to the Quality setting.  I've probably caused myself and other people some crashes with this, and I'm sorry about that.
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GalaxseeHiggs's avatar
bilobobobil's avatar

Wow, this tutorial is from 5 1/2 years ago, and it still addresses some questions in the current Daz Studio 4..15b version! Thank you.


SickleYield's avatar

You are very welcome :)

JelenaEllethil's avatar

Thank you for this tutorial. :)

Migitmd's avatar

While this is an older post, I've actually achieved 100% converged Ratio once or twice. I thought it was impossible, but the log file said otherwise.

The Render Quality doesn't actually 'override' time and sample counts- but does significantly impact quality, so no argument there. I have mine set to 1000, with 10,000 samples and 24 hr counts. the 10K samples are actually achieved 99.9% of the time (converged 100% twice).

my settings:

1800 secs for update (30 minutes)

10,000 samples (15K or higher for high resolution)

84600 secs for max time (24 hrs. hit this twice)

1000 render quality

100% converged ratio (I hit this twice)

They are set to extremes because i found that it's faster and produces better quality renders.

Wow, this works fine to me...

Iray (Convergence) : 99.98%

envixer's avatar
While rendering quality does increase time, it doesn't just do that:

A convergence estimate for a pixel has to reach a certain threshold before a pixel is considered converged. This attribute is a relative quality factor for this threshold. A higher quality setting asks for better converged pixels, which means a longer rendering time. Render times will change roughly linearly with the given value, i.e., doubling the quality roughly doubles the render time.

A Rendering quality setting of 1.5 reduces shadow noise visibly.

Look here for all you ever wanted to know about Iray options: www.migenius.com/doc/realityse…
EnglishBob's avatar
Thanks for that! Very helpful hints for an Iray beginner.
gocuzero's avatar
gracias ahora comprendo mucho mejor  el iray .
SickleYield's avatar
De nada.  Bien rendering. :)
LordDayradon's avatar
Hmm wish I read this first.  I have my convergence set to 100, and quality to 10.  My max time is capped at 3 hrs (as it was supposed to be a quick test :) yeah right)   Now, based on my results at currently 45% and 1hr 48m in, I don't think 3 hrs is long enough.  Visually I can tell the BG in relation to the focal distance is still way too pixelated.  Based on your entry above, does it mean that my 3hr cap, is actually 30hrs, since it's quality 10? or will it still stop at 3hr?  If it helps I've maxed out max samples at 15K (not sure how iterations in relation to that can derive the number of samples, but mine is 912 iterations roughly)
SickleYield's avatar
If quality settings are on it ignores the other time/samples settings totally.
LordDayradon's avatar
TY for the confirmation.  Coincidentally it finished after about 4 hrs.  BG still too pixleated.  Rerunning it now, but changed filter from gaussian to Mitchell.  Results are turning out much better, and it's been 6 hours roughly and still at 47%
SickleYield's avatar
If you're using the 4.11 beta there's also a Post Denoiser option in the Render Settings that's great for polishing out that irritating final grain.  I usually set mine to 500-1000 samples.
LordDayradon's avatar
I'm still on the latest release version. Lots of bad experiences with beta's etc.  I think the filter change has helped. a lot less grainy in the areas I was concerned about. It's at 48% 11 hrs in.  Should turn out very nice I think. BTW your light shafts tutorial was great!
SickleYield's avatar
Thanks, I'm glad you liked it!
This whole Iray setting page feels really odd. Why did they take out controlling the sample number from our hand? I'm used to blender cycles, where you can exactly tell you want 500 samples... Here it will be something like 300-800... Who knows? I often get different sample size with exactly the same settings.... And also have trouble with grainy transparent (like glass) stuff.... So I have to render like 3 times to get it right.

You guide helped a lot. By upping the rendering quality I get higher samples consistently. It helps with the grain.

Also in my experience you should turn off the CPU render if you are using Optix Acceleration. (Tested with GTX1080+ AMD FX 8150 and i7-4700HQ+GTX 860M. In both cases CPU being turned off resulted better render times.)
SickleYield's avatar
It is weird like that, definitely.  I've honestly never understood why the minimum sample number is a thing.

You get different samples for the same settings when you add/remove things from the scene that require more samples.  A scene with a refractive object, max time 1 hour, might only get to 5000 samples where one without that object would get to 8000 (numbers not correct, just for proportion).  Because the Max Time is controlling when the cutoff point is.  If you want samples to be the cutoff instead, turn off Quality and set Max Time to 0.  It should then render until the max number of possible samples is achieved.

I'll give it another look!  In my first trials having the CPU on still added a small amount of speed with OptiX on, but that was many versions ago now.
JasonMcCree's avatar
Hi SickleYield,

Thanks for this but i still have a few questions though.

You say: Rendering Quality: This linearly increases render time each time you raise the number: 2 is double the value of 1, 3 is triple the value of 1, etc.  It overrides the time and samples counts.  Use this only if you really want to try the "render forever and tell it to stop when I like how it looks" method. 

If this overrides the time....how can it increase the time?

I have been rendering on 4k and 99,9% with 10000 samples and 288000 (8 hours) and still look a bit granny but less granny then on 4 hours.

I'm using a GTX 970 4G.
My scenes have a lot of reflections, like water (from a bath) and shinny skin.

When the render after 8 hours is finished it looks okin 4k aslong as you don't zoom in. because then you can really see the grain.
i render at 4k because i though re sampling to 1080 would get rid of the grain abit but it has less effect then i would liek to see.

The grain is especially vissible in the darker areas where the skin moves from shinny to less shine with shadows.
I know iray like light and doens't like darkness.

So what would be best pratice here?
How would you set up the settings in the progressive render tab?

Because when i set render quality to 2 is still ran about 8 hours like it's set on max time 28800

Other question:

you said about 100 convergence can crash.
I set it to 100 last night before reading this and when i look in the log file is see the following warning:

WARNING: dzneuraymgr.cpp(307): Iray ERROR - module:category(IRAY:RENDER):   1.0   IRAY   rend error: Degraining filter cannot be combined with "black pixel filter

With my other renders beofre 100% convergence and before putting it to Quality 2 i didn't see this warnings.
So could this be an effect of setting it to 100% convergence or is this something else?

SickleYield's avatar
It increases the time BY overriding whatever the existing time value is.  The default time value isn't that big, so if you set Quality to 4 it can take four times as long as the default.

A 4k scene is not going to ever be fast unless you're running a Titan or something.  A standard Daz promo is only like 1000x1300.

There's probably nothing wrong with your settings.  You can let it run for 16-20 hours, or you can postwork for smoothness, that's about it.

Yes.  The error you got is probably a result of setting convergence at 100 even though it does not reference that directly.
AncientWire's avatar
Thank you.  This clears up a bit of my confusion about rendering :)
KCRileyGyer's avatar
Thank you for this even though I’ve had it in my favourites since you posted this. I have since discovered that if you set the Max Time (secs) to zero then the render won’t time out. After that, the render ending is reliant on Max Samples.
SickleYield's avatar
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